An error occurred while attaching module (Dynamicweb.Frontend.Content)

System.InvalidOperationException: Handler404.Handle() has already been called. Circular reference. /products?ProductID=PROD1229
   at Dynamicweb.Frontend.Handler404.Handle()
   at Dynamicweb.Ecommerce.Frontend.Frontend.EndRequestAs404()
   at Dynamicweb.Ecommerce.Frontend.Frontend.RenderProduct(Product product, String unitId)
   at Dynamicweb.Ecommerce.Frontend.Frontend.EcomRender()
   at Dynamicweb.Ecommerce.Frontend.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)